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A novel, 9XX nm fiber-coupled module using arrays of highly reliable laser diode bars has been developed. The module is capable of multi-kW output power in a beam parameter product of 80 mm-mrad. The module incorporates a hard-soldered, isolated stack package compatible with tap-water cooling. Using extensive, accelerated multi-cell life-testing, with more than ten million device hours of test, we have demonstrated a MTTF for emitters of >500,000 hrs. In addition we have qualified the module in hard-pulse on-off cycling and stringent environmental tests. Finally we have demonstrated promising results for a next generation 9xx nm chip design currently in applications and qualification testing

We report on our progress developing long wavelength high power laser diodes based on the InGaAsP/InP alloy system emitting in the range from 1400 to 2010 nm. Output power levels exceeding 50 Watts CW and 40% conversion efficiency were obtained at 1470 nm wavelength from 20% fill factor (FF) bars with 2 mm cavity length mounted on water cooled plates. Using these stackable plates we built a water cooled stack with 8 bars, successfully demonstrating 400 W at 1470 nm with good reliability. In all cases the maximum conversion efficiency was greater than 40% and the maximum power achievable was limited by thermal rollover. For lasers emitting in the range from 1930 to 2010 nm we achieved output power levels over 15 W and 20 % conversion efficiency from 20% FF bars with 2 mm cavity length on a conductively cooled platform. Life testing of the 1470 nm lasers bars over 14,000 hours under constant current mode has shown no significant degradation.

We report on the performance of our high power and high efficiency 14xx nm lasers in different formats as packaged on conduction cooled packages using soft solder. Single emitters exhibited output powers as high as 6 watts, while six emitter minibars output 20 W, and 20% fill factor (ff) bars provided over 40 W of output power. In all cases the maximum conversion efficiency was greater than 40% and the maximum power achievable was limited by thermal rollover. These same 20% ff bars output close to 90 W when operated quasi CW (QCW). Preliminary life testing of these bars for over 5000 hours under constant current mode has shown no significant degradation.

We report on room-temperature continuous-wave (CW) operation of lambda~8.2 mum quantum cascade lasers grown by metal-organic chemical vapor deposition without lateral regrowth. The lasers have been processed as double-channel ridge waveguides with thick electroplated gold. CW output power of 5.3 mW is measured at 300 K with a threshold current density of 2.63 kA/cm2. The measured gain at room temperature is close to the theoretical design, which enables the lasers to overcome the relatively high waveguide loss

Amplified spontaneous emission spectroscopy is used to extract the gain and refractive index spectra systematically. We obtain the gain and differential gain spectra using the Hakki-Paoli method. The refractive index profile, the induced change in refractive index by an incremental current, and the linewidth enhancement factor are measured from the Fabry-Perot peaks and the current-induced peak shifts in the amplified spontaneous emission spectra. The measured optical gain and refractive index are then compared with our theoretical model for strained quantum-well lasers. We show that a complete theoretical model for calculating the electronic band structure, the optical constant, and the linewidth enhancement factor agrees very well with the experiment. Our approach demonstrates that amplified spontaneous emission spectroscopy can be a good diagnostic tool to characterize laser diodes, extract the optical gain and index profiles, and confirm material parameters such as the strained quantum-well band structure parameters for a semiconductor structure under carrier injection.

A simple fitting technique based on the current balancing concept has been used to calculate the minority‐carrier diffusion length Ln in the base layer of an InP/InGaAs single‐heterojunction bipolar transistor grown by metalorganic chemical‐vapor deposition. Due to the emitter‐base surface‐related problem, the minority‐carrier lifetime was shown to be dependent on the collector current. This surface‐related problem could be a result of the high SiN deposition temperature used in the processing steps. The method predicts value for Ln of 0.97 μm at low collector current and 3.4 μm at high current.

The authors demonstrate theoretically and experimentally that the relative intensity noise (RIN) of laser diodes can be dramatically reduced by decreasing nonlinear damping in the laser. Four types of InGaAs/InP multiple quantum well (MQW) lasers with different well widths, barrier widths, and numbers of wells were fabricated. By comparing these four types of devices, it is shown that MQW lasers with wider wells, narrower barriers, and larger numbers of wells have smaller nonlinear damping and lower RIN. >

A report is presented on the growth and characterization of the first InGaAs-InP-based graded-index separate-confinement-heterostructure (GRIN-SCH) strained quantum-well lasers operating near 1.47 mu m. The structure features linearly graded InGaAsP waveguide layers for both optical and carrier confinement in a very narrow, strained quantum-well layers. The excellent structural quality of the active and waveguide regions has been confirmed by transmission electron microscopy (TEM) and secondary ion mass spectroscopy (SIMS) analysis results. Strained quantum-well lasers with well widths as narrow as 5-6 nm were fabricated with threshold current densities as low as 750 A/cm/sup 2/. Buried-heterostructure lasers based on strained quantum-well active lasers exhibit threshold currents as low as 10-15 mA with quantum efficiency of 70-80%. With antireflection coating on one side of the sample, the laser shows threshold current of 35 mA with highest output power of 160 mW. >

We report Buried-heterostructure QCLs of lambda~5mum, grown by MOCVD, with extremely low CW room-temperature threshold-current-density of 0.75kA/cm2. Slope efficiencies of 1079mW/A, output power of 116 mW at 288 K and internal loss of 1.84cm-1 have been achieved.

We report on room temperature, continuous wave operated Quantum Cascade lasers emitting around 8 μm wavelength. The lasers were grown by metal organic chemical vapor deposition. Lasers with and without lateral regrowth are compared. A continuous‐wave output power ∼ 5 mW is measured at 300 K for a metal‐clad laser, and 30 mW for the buried heterostructure laser. The measured gain at room temperature is close to the theoretical design, which enables the lasers to overcome the still high waveguide loss.

An electroabsorption modulated laser (EML) is linearized by emulation and reversal of the nonlinear distortion using a companion EML inside an optoelectronic interferometer. Suppression of composite second-order and triple-beat signals to

Room temperature, continuous-wave operation of lambda~8.2 mum quantum cascade lasers grown by MOCVD is reported. The lasers have been processed as double-channel ridge waveguides without the need for buried heterostructures.

We proposed and demonstrated an integrated device with a simple structure that can perform both transmitting and receiving functions with very high receiving sensitivity. The device is composed of a tunable distributed-Bragg-reflector (DBR) laser as a local oscillator (LO) and an integrated detector. An FSK receiver sensitivity of -43.4 dBm at 108 Mb/s was obtained. Multichannel operating characteristics were studied and it was found that systems with an operation channel spacing of 3 GHz can be realized. This device can be operated with either half-duplex or full-duplex mode for broad-band access applications.

We report on the generation of short optical pulses from a novel additive pulse mode-locked (APM) semiconductor quantum well laser. Transform-limited optical pulses with durations of 8 ps and peak powers of 43 mW are achieved at a repetition rate of 35 GHz.

Coherent communication is one of the very few promising technologies that can provide a huge amount of channels and dynamically allocate the bandwidth for massive number of users.

We report in this work a record low threshold (∼4 mA, cw), 1.55 μm wavelength, grating‐coupled surface‐emitting laser (GCSEL) which rivals all other existing SELs in the 1.3 or/and 1.55 μm regions. Methods to improve the asymmetric far‐field patterns and to obtain even lower threshold SELs are also demonstrated and/or suggested.

The first monolithically integrated DFB laser/Mach-Zehnder interferometric modulator fabricated by the selective area low pressure MOVPE growth technique is reported. A near 3-dB power divider at the Y-branches of the interferometer has been reproducibly achieved by a photolithographically defined dielectric mask used in the selective area growth technology and confirmed by an infrared near field imaging technique. A modulation depth of over 12 dB was achieved both in the forward and reverse bias to the arms of the phase modulator. >

A packaged hybrid soliton pulse source is used in a soliton transmission experiment employing sliding-frequency guiding filters. The source shows excellent stability and very clean tuning characteristics. Control of the operating frequency and wavelength are described. Error free transmission at 10 GBit/s is achieved over a distance of 27000 km. >

We describe hybrid lasers combining a semiconductor gain section and fiber cavity with integrated chirped Bragg reflector. These devices have produced output powers of 27.5 mW in a narrow linewidth (400 KHz) stable single longitudinal mode. The use of a chirped reflector to stabilize the single mode output, and correct grating orientation are described. The laser output has a side‐mode suppression ratio of over 55 dB at 27.5 mW output, and relative intensity noise (RIN) below 160 dB/Hz.

Coherent WDM communication systems have a great potential to be applied to local broadband access networks due to their high sensitivity and densely spaced multichannel characteristics. Unfortunately, compared with a high-bit-rate direct detection system the installation cost of such a system is relatively high. Although the hybrid coherent system can reach almost shot noise limited sensitivity, the higher cost can prevent it from gaining ground in the long run. In this work, we report a high sensitivity integrated coherent receiver with very simple device structure. The fabrication process of this device is so simple that it involves virtually no more than making a distributed-Bragg-reflector (DBR) laser. The device structure and its possible application as a broadband access terminal device with both receiving and transmitting functions are shown. The device is composed of a tunable DBR laser and an integrated detector. The incoming ASK or FSK signals are mixed in the DBR local oscillator (LO) cavity.

Coherent communication system has well-known advantages of high receiver sensitivity, high channel packing density, and flexibility in channel selection. Implementation of coherent detection in optical subscriber network for TV distribution and broad-band ISDN services have been demonstrated. Monolithically integrated coherent receivers is attractive for such applications, due to the dramatic cost reduction by eliminating packaging of hybrid components. However, the device structure as well as fabrication process of integrated receivers are usually quite complex and the yield is considerably low. We proposed and demonstrated an integrated device with simple structure can perform both transmitting and receiving functions with very high receiver sensitivity. The device structure and possible configurations as customer transceiver in coherent multi-carrier (CMC) distribution system is shown. The device is composed of a tunable DBR laser as a local oscillator (LO) and an integrated detector. This allows one to fully utilize the wavelength tuning range to achieve highly dense spaced WDM coherent systems.

Very low threshold (/spl sim/4 mA), grating coupled, surface-emitting lasers around 1.55 /spl mu/m wavelength region are reported. Emitting far field profiles in different directions have been measured for either single- or multi- mode laser cases. Future directions to improve FWHM of the laser emitting angles are also discussed. >

Summary form only given. This talk reviews high speed sources for present and future communication links. We describe directly modulated DFB and Fabry-Perot lasers suitable for 2.5 and 10 GBit/s systems, together with analog links from dc to 20 GHz. Next generation integrated DFB/electro-absorption modulator devices and high performance optical pulse sources will be discussed.

We demonstrate a very low threshold 1.55 /spl mu/m grating coupled surface emitting laser (GCSEL) with a CW room temperature threshold of only 6 mA. The laser structure is a multi-quantum well distributed-feedback (DFB) laser with a second order grating buried under the gain medium. The laser is fabricated by following the capped-mesa buried heterostructure (CMBH) process with a stripe width of around 0.9 to 1.2 /spl mu/m wide. We have measured the FWHM of the far field intensity profile of the laser.

Subpicosecond transform-limited optical pulses are generated from monolithic colliding pulse mode-locked multiple quantum well lasers at 1.5- mu m wavelength. The 0.95-ps optical pulses are synchronized with a millimeter-wave oscillator up to 40 GHz and have a modulation depth greater than 95%. Using a passive mode-locking technique, 610-femtosecond optical pulses are also generated at a repetition rate as high as 350 GHz without any synchronization sources. This is the highest pulse repetition rate ever reported for semiconductor optoelectronic sources. >

In conclusion, a new detection scheme using integrated heterodyne transceiver with counter-mixing operation was experimentally investigated. A received power sensitivity of-32 dBm at 100 Mb/s was obtained. A simple theoretical model to optimize the receiver sensitivity was developed. Different full-duplex operation schemes were discussed. The counter-mixing mode heterodyne receivers could be a good candidate for broadband coherent access networks.

To manage a WDM network, the signal at each wavelength channel must be constantly monitored, and the power of each channel should be individually controlled to provide a reliable, user friendly system. Although terminal devices (such as detectors) can monitor, an optical in-line device that can perform both the monitoring and controlling function would be optimal. In this paper, we present the experimental results of using an integrated tunable active filter as just such a useful device.

We proposed and demonstrated a new and very simple technique of varying the lasing wavelength of distributed feedback (DFB) lasers with the need for fabricating gratings with different pitches. This is accomplished by angling the active stripe at an oblique angle with respect to the axis of the grating lines. This technique should be particularly suitable for fine tuning of lasing wavelength, and it eases the stringent demand on precise control of absolute grating pitches. It should be useful and important for dense (wavelength division multiplexing (WDM) applications and monolithic integration of multi-wavelength DFB lasers. >

We compare the dynamic properties of bulk, lattice‐matched, and strained multiple quantum well (MQW) 1.3 μm Fabry–Perot lasers up to high‐bias levels. We show for the first time that long wavelength strained MQW lasers can have a higher intrinsic bandwidth than bulk active and lattice‐matched MQW lasers, and that a −3 dB bandwidth of over 30 GHz can be expected from devices with a thin separate confinement heterostructure if a low parasitic device structure is used. The K factor used to determine maximum bandwidth in bulk active laser diodes is shown to be unsuitable for strained MQW devices, where a linear relationship of damping/(resonance frequency)2 is not observed at high power levels.

We compare the temperature dependent characteristics of multiple quantum well semiconductor laser diodes and light emitting diodes operating at a wavelength, λ=1.3 μm. No model in which Auger recombination is the dominant temperature sensitive parameter can explain our experimental observations. We suggest that net gain is the appropriate temperature dependent variable which determines laser diode performance at elevated temperatures.

A new approach to reduce the rates of threshold current increase and external quantum efficiency decrease with increasing temperature in a semiconductor laser is proposed and demonstrated. This is based on the realization that the total laser cavity loss, which is normally relatively independent of wavelength, can be made to decrease with increasing wavelength. Since the gain peak of the laser shifts towards longer wavelength as temperature is increased, the rate of threshold current increase is thus reduced with increasing temperature. To implement this, we proposed and demonstrated the broadband enhanced feedback (BEF) approach using multilayer coatings, very weak or chirp gratings with peak reflectivity centered at the lasing wavelength corresponding to the maximum operating temperature desired. It was shown that the threshold‐temperature coefficient T0 improved from the typical value of ∼45 K in long wavelength InGaAsP lasers (bulk active or MQW) to 85 K in BEF coated lasers. This scheme also simultan...

High performance InGaAsP/InP multiquantum well (MQW) buried heterostructure lasers emitting around 1.3 μm were prepared for the first time by chemical‐beam epitaxy. At 20 °C, continuous‐wave (cw) threshold currents were 5–8 mA and quantum efficiencies were 0.35–0.45 mW/mA for 250 μm long lasers having one facet ∼85% reflective coated. At 80 °C, the cw threshold currents remained low, 23 mA, quantum efficiency stayed high, 0.22 mW/mA, and output power of ∼10 mW was achieved. cw power output as high as 125 mW was achieved with 750 μm long lasers having AR–HR (∼5%–85%) coatings. Lasers with bulk active were also studied for comparison. Though they also have excellent device performance, in general, they are somewhat inferior to MQW lasers.

We demonstrated the first successful growth of 1.5 μm strained‐layer InGaAs/InGaAsP multi‐quantum‐well (MQW) distributed feedback (DFB) lasers by chemical beam epitaxy (CBE). In these DFB wafers, a quaternary grating is placed at the bottom of the MQW stack with an InP spacer layer. Studies by transmission electron microscopy show that defect‐free InP regrowth was achieved with no mass transport needed over the grating corrugations before regrowth. With CBE regrowth the shapes of the gratings were well preserved. The InP overlayer also very effectively smoothed out the quaternary surface corrugations resulting in very flat MQW structures. Buried‐heterostructure 6‐QW DFB lasers (250 μm long and as‐cleaved) operated at 1.55 μm with cw threshold currents 10–15 mA and slope efficiencies up to 0.35 mW/mA (both facets). Side‐mode suppression ratios (SMSR) as high as 49 dB was obtained. The laser operated in the same DFB mode with SMSR staying above 40 dB from threshold and throughout the entire current range even at high temperatures (70 °C checked).

A semiconductor laser amplifier (SLA) has been employed successfully for optical demultiplexing in two-channel optical time division multiplexed system experiments at 6 and 2 Gb/s. Demultiplexing of 6-Gb/s (2-Gb/s) signals was demonstrated with a power penalty of 1.6 dB (3.0 dB) at bit error rates of 10/sup -9/. It is also shown that a reduction of the generated amplified spontaneous emission can be obtained by optical gating/demultiplexing for systems incorporating inline amplifiers. A 0.5-dB improvement in sensitivity was achieved as a result of using an SLA for demultiplexing from 2.0 to 1.0 Gb/s in a system with one inline Er/sup 3+/-doped fiber amplifier. >

The use of all‐gaseous doping during chemical‐beam epitaxy (CBE) offers several important advantages. Injection of dopants, together with the metalorganic group‐III beam, automatically leads to uniform dopant distribution across the entire wafer. Vapor dopant sources also ensure long‐term stability and reproducibility. It also allows for instant doping profile control. Most important of all, an all‐gaseous doping CBE system is particularly attractive for system manufacture and device production applications. We investigated n‐ and p‐type dopings in InP and InGaAs during CBE using tetraethyltin (TESn) and diethylzinc (DEZn), respectively, and confirmed their suitability for use in growing high‐quality long‐wavelength InGaAs(P)/InGaAsP semiconductor injection lasers. Buried heterostructure lasers fabricated from CBE‐grown 1.5‐μm six quantum‐well base wafers and metalorganic vapor‐phase‐epitaxy regrown iron‐doped InP have excellent current‐voltage characteristics and threshold currents as low as 8 mA. cw operation with threshold current as low as 23 mA at 80 °C and output power of ∼10 mW was achieved for diodes having one facet ∼85% reflective coated.

Low‐threshold and high‐output power of the first InGaAsP/InP graded index strained multiple quantum well lasers emitting near 1.3 μm wavelength is reported. A continuous wave threshold current of 10 mA and a quantum efficiency of 60% with maximum output power of 100 mW/facet is observed in uncoated lasers having compressively strained InGaAsP quantum wells. With high reflectivity on both facets, a reduced threshold current as low as 3.5 mA is observed. Highest output power of 250 mW was observed in lasers with antireflection‐high reflection coating configuration operating at 10 °C. The improved performance of the lasers is attributed to both the reduced internal absorption loss (6 cm−1) and the suppressed nonradiative recombination in the structure.

The threshold current density, internal quantum efficiency, internal loss, and emission wavelength of InGaAsP/InP multiquantum well lasers, grown by atmospheric pressure metalorganic chemical vapor deposition, were measured as a function of substrate orientation on and away from the (001) towards the nearest [011] and [111]A. The laser parameters are optimized for (001) oriented substrates. Substrate misorientations of more than 3° in either direction yield lasers with increased threshold current density and lower internal quantum efficiency. The internal loss increases and the surface morphology becomes visually poorer for substrate misorientations of 6°. The laser emission shifts to longer wavelength with increasing misorientation.

The intensity noise of strained InxGa1−xAs/InP multiple quantum well (MQW) lasers is measured for three types of strain: tensile strain (x=0.48), no strain (x=0.53), and compressive strain (x=0.65). From a comparison between the measured noise power spectral density and the theoretical one, the resonance frequency and the carrier damping factor of each type of lasers are calculated. Although compressive strained MQW lasers show abot 10% increase in resonance frequency compared to those of tensile strained and unstrained lasers, this increase is smaller than theoretically predicted. Most important, all three types of MQW lasers show about two to three times higher nonlinear gain saturation and lower maximum bandwidth than conventional double‐heterostructure lasers. A solution to reduce this high damping is also discussed.

A survey of graded‐index separate confinement multiple quantum well distributed feedback lasers comparing the effects of strain in the quantum well upon threshold, output power, and linewidth is reported. Lasers with either compressive or tensile strained quantum wells and a long cavity length (890 μm) show lower threshold current (10–20 mA) as well as lower linewdith power product than lasers with unstrained quantum wells and have a comparable minimum linewidth to the unstrained quantum well lasers. A minimum linewidth as narrow as 900 and 440 kHz for compressive strain and unstrained quantum well lasers, respectively, was obtained at output power of 30 mW. Single longitudinal mode operation with a maximum output power over 80 mW was observed in all the structures.

We have demonstrated the first successful preparation of InGaAs/InGaAsP multiple quantum well (MQW) lasers grown by chemical beam epitaxy. The broad‐area threshold current densities of standard (not graded index) separate confinement heterostructure (SCH) MQW lasers were as low as 860 and ∼590 A/cm2 for cavity lengths of 500 and 1500–3500 μm. Such values are similar to those obtained from MQW wafers employing the more advanced graded index SCH(GRIN‐SCH) grown by metalorganic vapor phase epitaxy. Buried‐heterostructure lasers also have similar threshold currents, i.e., 25–40 mA for 300–1500 long cavities. Pulsed and cw output power at 1.57 μm as high as 216 and 140 mW were obtained from 1‐mm‐long buried‐heterostructure lasers having antireflection and high reflection coatings of ∼5% and ∼85%. The layer thickness uniformity is better than ±1% across a 2‐in.‐diam wafer.

We describe, for the first time, the preparation of InGaAs/InP homojunction confined buried‐heterostructure lasers by high vacuum processing techniques. Lithography and waveguide mesa etching were carried out using ultrathin native oxide masking, focused Ga ion beam writing, and free Cl2 etching. Base laser structures and overgrowth were carried out by atmospheric pressure metalorganic vapor phase epitaxy. The resulting lasers have low‐threshold currents of ∼62 mA.

We describe InGaAs/InP multiquantum well distributed feedback (DFB) lasers with novel properties atrributable to the quantum well based active layer. The low internal loss waveguide and shallow gratings have allowed the fabrication of lasers with a cavity length varying from 0.5 to 2 mm, and corresponding threshold currents of 22 and 100 mA, respectively. A mode rejection ratio as high as 50 dB has been obtained in lasers with one antireflection‐coated facet. The long cavity devices exhibit linewidths as low as 600 kHz at a power output of 35 mW. Transmission experiments through 70 km of fiber, at 1.7 Gb/s, showed a dynamic chirp penalty of only 0.25 dB, a factor of 8–10 smaller than in conventional lasers.

A record high power output strained‐layer InGaAs/InP quantum well laser emitting at 1.48 to 1.51 μm is demonstrated. Maximum cw output as high as 206 mW is obtained from a sample with a cavity length of 890 μm and a facet reflectivity of ∼5 and 85% for the front and the rear facets, respectively. The laser has a threshold of 30 mA and a slope efficiency as high as 0.4 mW/mA.

Quantum well lasers based on strained InxGa1−xAs/InP were grown by atmospheric pressure metalorganic vapor phase epitaxy. Buried‐heterostructure lasers with the active layer consisting of three quantum wells, each ∼50 A thick, placed in a continuously graded waveguide, exhibit threshold currents as low as 15 mA, high quantum efficiency (24%), and power output (∼100 mW), independent of composition. Changing the In concentration from x=0.48 to 0.62 results in the lasing wavelength shift from 1.45 to 1.62 μm. These wavelengths are in excellent agreement with the calculated energies of the electron–heavy hole exciton transition.

An InGaAs metal-semiconductor-metal (MSM) photodetector with an Fe-doped InP Schottky barrier enhancement layer is described. With 5-V bias, the detector has negligible low-frequency gain, a low dark current of 200 nA, a responsivity of 0.3 A/W, and an impulse response with a 1/e fall time of 65 ps, corresponding to a 3 dB bandwidth of 2.5 GHz. The device layer structure is a very attractive candidate for integration with high-performance InGaAs/InP FETs. >

We report a new generation switch, the data-block switch, which can greatly increase the capacity and reduce the complexity of the interconnect network of a parallel computing system. By using WDM techniques, parallel data can be multiplexed and transmitted through a single fiber. By using photonic switching techniques, we can switch a block of parallel data in one switch operation to any site desired. In this work, we demonstrate such an operation with our fabricated 1 X 2 semiconductor optical amplifier (SOA) switch. This integrated device is an active/passive Y- junction waveguide device with a passive waveguide region in the middle and 3 active waveguide regions at each end. The amplified spontaneous emission spectrum of the SOA shows that this broadband switch can easily cover a wavelength range of more than 64 ITU wavelength grids (100 GHz). The switch operation of multiple wavelengths and the switching speed of the device were studied. A switching time of around 400 ps was achieved.

Integrated multi-section distributed-Bragg-reflector filters were employed as channel filters, channel power monitors, and channel power controllers/equalizers in a WDM system. The tunable active filter we used was an integrated 4-section InGaAs/InGaAsP DBR laser biased below threshold. Experimental results on an 8-channel WDM system are reported. With this simple and integrated structure, the cost to implement a WDM network monitoring and control system can be greatly reduced.

The generation of short optical pulses at 1.5 /spl mu/m is a key issue in future communications systems. Recently, a new approach to pulse generation has been reported in which the output ofa CW laser is converted to nearly transform limited pulses by a sinusoidally driven electro-absorption modulator. This simple technique is readily integrated and provides flexibility in both operating frequency and wavelength, an important asset for soliton and optical time division multiplexing (OTDM) applications.

Monolithic cavity colliding pulse mode-locked (CPM) semiconductor lasers have been shown to give excellent performance1 and show promise for high bit rate communications systems. In this paper, the performance of the CPM configuration is compared with that of the self-colliding pulse configuration (SCPM) shown in Fig. 1. The SCPM configuration is one half of the CPM configuration, with a high reflectivity coating placed on the half-length saturable absorber. In CPM, two separate pulses of energy E collide in the center saturable absorber. In SCPM a pulse of energy E collides with itself in the half-length absorber. The performance of the two devices should be identical due to the symmetry of the two configurations. Both structures should therefore take equal advantage of the colliding pulse benefits.2-3 SCPM offers half the repetition rate for the same length device and a lower drive current at the expense of a high reflection coating. CPM devices are found to be very sensitive to asymmetrical cleaves whereas SCPM devices have guaranteed symmetry.